CVE-2021-21259
Stored XSS in slide mode
HedgeDoc is open source software which lets you create real-time collaborative markdown notes. In HedgeDoc before version 1.7.2, an attacker can inject arbitrary JavaScript into a HedgeDoc note, which is executed when the note is viewed in slide mode. Depending on the configuration of the instance, the attacker may not need authentication to create or edit notes. The problem is patched in HedgeDoc 1.7.2. As a workaround, disallow loading JavaScript from 3rd party sites using the Content-Security-Policy header. Note that this will break some embedded content.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- None
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Stored XSS in slide mode
HedgeDoc is open source software which lets you create real-time collaborative markdown notes. In HedgeDoc before version 1.7.2, an attacker can inject arbitrary JavaScript into a HedgeDoc note, which is executed when the note is viewed in slide mode. Depending on the configuration of the instance, the attacker may not need authentication to create or edit notes. The problem is patched in HedgeDoc 1.7.2. As a workaround, disallow loading JavaScript from 3rd party sites using the Content-Security-Policy header. Note that this will break some embedded content.
- Record
CVE-2021-21259- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
EUVDEUVD-2021-8640
HedgeDoc is open source software which lets you create real-time collaborative markdown notes. In HedgeDoc before version 1.7.2, an attacker can inject arbitrary JavaScript into a HedgeDoc note, which is executed when the note is viewed in slide mode. Depending on the configuration of the instance, the attacker may not need authentication to create or edit notes. The problem is patched in HedgeDoc 1.7.2. As a workaround, disallow loading JavaScript from 3rd party sites using the Content-Security-Policy header. Note that this will break some embedded content.
- Record
EUVD-2021-8640- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N - Updated
- 2026-11-03
NVD
HedgeDoc is open source software which lets you create real-time collaborative markdown notes. In HedgeDoc before version 1.7.2, an attacker can inject arbitrary JavaScript into a HedgeDoc note, which is executed when the note is viewed in slide mode. Depending on the configuration of the instance, the attacker may not need authentication to create or edit notes. The problem is patched in HedgeDoc 1.7.2. As a workaround, disallow loading JavaScript from 3rd party sites using the Content-Security-Policy header. Note that this will break some embedded content.
- Record
CVE-2021-21259- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N - CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:P/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
OSV
HedgeDoc is open source software which lets you create real-time collaborative markdown notes. In HedgeDoc before version 1.7.2, an attacker can inject arbitrary JavaScript into a HedgeDoc note, which is executed when the note is viewed in slide mode. Depending on the configuration of the instance, the attacker may not need authentication to create or edit notes. The problem is patched in HedgeDoc 1.7.2. As a workaround, disallow loading JavaScript from 3rd party sites using the Content-Security-Policy header. Note that this will break some embedded content.
- Record
CVE-2021-21259- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-21259 is a high vulnerability (CVSS 7.4) in Hedgedoc, published January 22, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.37%, the 72nd percentile. No source names a fixed version.